#include<stdio.h>
#include<unistd.h>

int g_val = 100;

int main()
{
    pid_t id = fork();
    if (id == 0)
    {
        int cnt = 0;
        //child
        while(1)
        {
            printf("I am child,pid:%d,ppid:%d,g_val:%d,&g_val:%p\n",getpid(),getppid(),g_val,&g_val);
            sleep(1);
            cnt++;
            if (cnt == 5)
            {
                g_val = 200;
                printf("child change g_val 100 -> 200 success\n");
            }
        }
    }
    else
    {
        //father
        while(1)
        {
            printf("I am father,pid:%d,ppid:%d,g_val:%d,&g_val:%p\n",getpid(),getppid(),g_val,&g_val);
            sleep(1);
        }   
    }
    return 0;
}
